Method of measuring the electric conductivity of body fluids, and test probe for carrying out the method

ABSTRACT

A method of measuring the electric conductivity of body fluids. It uses several test electrodes positioned at various sites at one area of the body to determine electric resistance. The measurements are obtained with a test probe that accommodates the test electrodes. The resistances detected by the test electrodes are polled and the minimal resistance is exploited as a reference for determining electric conductivity. The test probe employed to carry out the method is characterized by a large number of point-shaped test electrodes distributed over the surface of the test probe and associated with the same grounding device.

BACKGROUND OF THE INVENTION

The search for satisfactory methods of detecting estrus in farm animalshas long been a subject of scientific interest. The same is true withrespect to detecting the exact moment of ovulation in women.

SUMMARY OF THE INVENTION

To establish the optimal moment for insemination in farm animalsresearch has been undertaken to discover ways of exploiting hormoneanalysis, changes in the electric conductivity of the vaginal mucousmembrane, vaginal pH, vaginal cytology, and body temperature. Up to now,however, there are hardly any practical methods.

European Patent 0 177 994 describes a method of predicting ovulation inwomen. The beginning of menstruation is recorded and a body parameterthat regularly supplies information about the menstrual cycleestablished. This parameter is the specific electric resistance of thesubject's saliva. The document also proposes determining the electricresistance of the vaginal mucus at the beginning of determination of thefirst peak in the chart of the salivary resistance, whereby the vaginalelectric resistance is maintained daily. The increase in vaginalresistance subsequent to a minimum simultaneously indicates to the userthe presence of ovulation. The publication describes in this context atest probe for determining the electric resistance of the saliva. Thetest probe has a flat surface with several circular test electrodesembedded in it. The same publication describes a cylindrical test probesurrounded by annular test electrodes and with rounded ends fordetermining the electric resistance of the vaginal mucus. The testelectrodes in both test probes measure parallel.

One object of the present invention is an exact method of measuring theelectric conductivity of body fluids. The second is a test probe thatcan be practically employed in conjunction with the method.

The method of measuring the electric conductivity of body fluids inaccordance with the invention uses several test electrodes positioned atvarious sites at one area of the body to determine electric resistance.The measurements are obtained with a test probe that accommodates thetest electrodes. The method is characterized in that the resistancesdetected by the test electrodes are polled and the minimal resistance isexploited as a reference for determining electric conductivity.

The invention takes into account that the test probe and hence the testelectrodes constantly change position relative to the adjacent body walldue to the motion of the human or other animal during the measurement ofthe electric conductivity of body fluids, especially during themeasurement of the electric conductivity of vaginal or cervical mucus.The test electrodes will accordingly more or less contact the bodyfluid. The desired signal is accordingly powerfully affected by thevolume and spatial distribution of the mucus. It depends, in otherwords, on the position of the testing site. The method in accordancewith the invention counteracts this dependency first by measuring atseveral different sites within the area. Changes in signal due tochanges in the electric conductivity of the mucus must accordinglyappear as tendencies at each site. The various sites are obtained bypositioning a large number of test electrodes. Since each test electrodeis separately circuited it is possible in order to determine theresistance to evaluate only the test electrode that has the lowestresistance.

Evaluation of the lowest resistance provides information as to whetherthe particular test electrode is taken into consideration that is mostwashed with mucus and accordingly lies in the freshest mucus. In termsof determining ovulation it is known that the electric resistance of thecervical and/or vaginal mucus is highest prior to ovulation anddecreases as ovulation approaches while the volume of mucussimultaneously increases when necessary. The low resistance due tooptimal positioning of the single test electrode being exploited forevaluation and the tendency toward decreased resistance at the approachof ovulation correlate therewith. Thus, due to the method in accordancewith the invention one attains high independence of mucous volume andposition of test probe or test electrodes, whereby one can assume thatthe test electrode with the lowest resistances is completely soaked inbody fluid. This value is exploited to construct an algorithm.

In practical terms there occurs with the test electrodes apoint-by-point measurement, meaning that point-shaped test electrodesare employed. Measurement of conductivity occurs in practical terms inthe form of long-term measurement at defined intervals. Thereaccordingly occurs a continuous detection of the conductivity of thebody fluid. The electric resistances are stored and can be subsequentlyprocessed. Measurement of the test electrodes with subsequent detectionof the lowest resistance can for example be carried out at intervals asbrief as a quarter, half, or whole minute.

Since body fluids are as a general rule electrolytes, which isespecially true of mucus, measurement must be carried out withalternating current to prevent polarization. The detected resistancewill accordingly not present itself as strictly ohmic but in the form ofimpedance. The method should be designed to ensure that the result willbe an absolute impedance magnitude.

It is considered particularly advantageous when in addition to detectingthe electric conductivity of the body fluid, ion releases in the bodyfluid and/or body temperature are detected. The detection of thesereferences should occur in particular during the determination ofovulation.

The test probe preferably employed to carry out the method features alarge number of point-shaped test electrodes distributed over thesurface of the test probe and associated with the same grounding device.When one considers that the current flowing between one pair ofconductors, specifically the point-shaped test electrode and itsassociated frame, is not restricted to the shortest path but distributesitself over all available paths, the result is two advantageousembodiments of the test probe. The first exhibits concentric with theparticular point-shaped test electrode a conductive grounding ring,whereby a ring of insulation is positioned between the pair ofconductors comprising the point-shaped test electrode and its associatedgrounding ring. The second has a ring of insulation around eachpoint-shaped test electrode and the remaining surface of the test probehas a conductive grounding surface. The probe support for thepoint-shaped test electrodes and the grounding rings or conductivegrounding surface are naturally made of insulating material. To preventsignal changes due to oxidation processes the point-shaped testelectrodes and the grounding rings or grounding surface are made of anon-oxidizing conductive material, gold for example.

If the test probe is inserted into the vagina, it is for practicalpurposes cylindrical with rounded ends or in the form of a ball. It canalso exhibit ion-sensitive test electrodes and/or temperature testelectrodes embedded in its surface. The evaluation units can beaccommodated inside the test probe so that they can be read into amemory subsequent to removal of the test probe from the body. It is onthe other hand also possible to establish an electric connection betweenthe test probe and the evaluation units positioned outside the body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 3 represent details with reference to two possibleembodiments of the test probe in accordance with the invention and ofthe method in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a top view of a cylindrical test probe 1 with rounded ends.Regularly position, at the same distance from one another, that is, overthe probe surface 2 are a number of point-shaped test electrodes 3. Eachpoint-shaped test electrode 3 is surrounded by a ring 4 of insulationthat is itself surrounded by a grounding ring 5 concentric withpoint-shaped test electrode 3. Point-shaped test electrodes 3 andgrounding rings 5 are gold. Grounding rings 5 are connected by lines 6.Point-shaped test electrodes 3 are connected separately. The connectionbetween test probe 1 and external assemblies not illustrated morespecifically in this figure is represented by a connecting cable 7.

The test probe 1 illustrated in FIG. 2 is essentially similar to the oneillustrated in FIG. 1. It has point-shaped test electrodes 3 surroundedby rings 4 of insulation on its probe surface 2. Instead of groundingring 5, the rest 8 of the test-probe surface between rings 4 ofinsulation exhibits a conductive grounding surface. This and thepoint-shaped electrodes consist of gold. In contrast to the embodimentillustrated in FIG. 1, a processing-and-memory unit for the detectedmeasurement values is accommodated in test probe 1. The values arerepresented subsequent to removal of test probe 1 from the body opening.

FIG. 3 is a block diagram for estrus detection, for detecting estrus incows for example. Impedance channels 11 corresponding to the number ofpoint-shaped test electrodes 3, sixteen impedance channels for example,are transmitted to an alternate-to-direct current converter 12 through amultiplexer 10. From the sixteen values, which are initially depositedin an intermediate buffer 13, an arithmetic unit (ALU) 14 determines thevalue with the lowest impedance. This selected impedance value isdeposited in an internal memory 15. A serial interface stores either ashort high-frequency transmission section or an inductive transmission16. External reading equipment intercepts the content of the memoryevery day and processes the data for estrus detection. Characteristic ofestrus is a definite drop in the impedance curve from approximately 60ohms to approximately 10 to 20 ohms, which basically follows theanimal's temperature curve. A current-saving circuit should be providedto ensure the reliability of the circuit for thirty-five days.

The overall circuit comprises several components:

Sensor

Mixed analog-digital ASIC: Amplifier, multiplexer, ac-dc converter, ALUunit (logic gate), RAM

Discrete technology: Inductive transmission or high-frequencytransmitter

Reading equipment consisting of: Receiving section (inductive orhigh-frequency), μ processor, long-term memory, input-output units

Sensor, ASIC, and telemetry section should be constructed miniaturizedso that introduction into the cow's vagina is possible. In thisapplication the complete size of the sensor should be matched to theparticular vaginal configuration.

A corresponding design of the test probe with smaller dimensions isemployed to detect ovulation in women, and furthermore an appropriateprocessing circuit. The test probe consists on the whole ofphysiologically unobjectionable material.

I claim:
 1. A method for measuring electrical conductivity of bodyfluids comprising the steps of: positioning a plurality of testelectrodes at various sites on one area of a body to determineelectrical resistance; taking measurements with said test electrodes;detecting resistances by said test electrodes; evaluating saidresistances detected by said test electrodes and obtaining a minimalresistance; designating the minimal resistance as a reference fordetermining electrical conductivity; and providing a common ground forsaid test electrodes, whereby the electrical conductivity of body fluidsis measured through said test electrodes.
 2. A method as defined inclaim 1, wherein a point-by-point measurement is taken with the testelectrodes.
 3. A method as defined in claim 1, wherein a measurement ofconductivity is taken in form of long-term measurements at specificintervals.
 4. A method as defined in claim 1, wherein said intervals area quarter, half, or whole minute.
 5. A method as defined in claim 1,wherein the body fluid is cervical and/or vaginal mucus of human and/orother animal, said measurements occurring said test electrodes in acervix or vagina for detecting estrus or determining ovulation.
 6. Amethod as defined in claim 1, wherein a measurement is carried out withalternating current and the resistance comprises impedance.
 7. A methodas defined in claim 1, wherein said measurement is in form of anabsolute impedance magnitude.
 8. A method as defined in claim 1,including the step of detecting ion releases in the body fluids and/orbody temperatures in addition to detecting electrical conductivity ofthe body fluids.
 9. An arrangement for measuring electrical conductivityof body fluids, comprising a plurality of test electrodes positioned atvarious sites on one area of a body to determine electrical resistance;means for taking measurements with the test electrodes; means fordetecting electrical resistances by said test electrodes; means forevaluating said resistances detected by said test electrodes andobtaining a minimal resistance, said minimal resistance being designatedas a reference for determining electrical conductivity; common groundingmeans, said test electrodes being point-shaped and distributed over asurface of said arrangement and associated with said common groundingmeans, whereby the electrical conductivity of body fluids is measuredthrough said test electrodes.
 10. An arrangement as defined in claim 9,wherein said grounding means comprises a conductive grounding ringconcentric to a respective point-shaped test electrode; a ring ofinsulation positioned between a pair of conductors comprising saidrespective point-shaped test electrode and said grounding ring.
 11. Anarrangement as defined in claim 10, wherein the point-shaped testelectrodes and respective grounding rings are made of a non-oxidizingconductive material.
 12. An arrangement as defined in claim 11, whereinsaid non-oxidizing conductive material is gold.
 13. An arrangement asdefined in claim 9, including a ring of insulation around eachpoint-shaped test electrode, said test probe having a remaining surfacewith a conductive grounding surface.
 14. An arrangement as defined inclaim 9, wherein said test probe is cylindrical with rounded ends. 15.An arrangement as defined in claim 9, wherein said test electrodes areion-sensitive.
 16. An arrangement as defined in claim 9, wherein saidtest probe is cylindrical with ball-shaped ends.
 17. An arrangement asdefined in claim 9, wherein said test electrodes are temperature sensingelectrodes.
 18. An arrangement as defined in claim 9, wherein said testelectrodes are ion-sensitive and temperature sensitive.
 19. Anarrangement for measuring electrical conductivity of body fluids,comprising a plurality of test electrodes positioned at various sites onone area of a body to determine electrical resistance; means for takingmeasurements with the test electrodes; means for detecting electricalresistances by said test electrodes; means for evaluating saidresistances detected by said test electrodes and obtaining a minimalresistance, said minimal resistance being designated as a reference fordetermining electrical conductivity; common grounding means, said testelectrodes being point-shaped and distributed over a surface of saidarrangement and associated with said common grounding means; saidgrounding means comprising a conductive grounding ring concentric to arespective point-shaped electrode; a ring of insulation positionedbetween a pair of conductors comprising said respective pointshaped testelectrode and said grounding ring; a ring of insulation around eachpoint-shaped test electrode, said test electrodes having a remainingsurface with a conductive grounding surface; said point-shaped testelectrode and respective grounding rings being made of a non-oxidizingconductive material; said test electrodes being cylindrical with roundedends; said test electrodes being ion-sensitive andtemperature-sensitive, whereby the electrical conductivity of bodyfluids is measured through said test electrodes.